The field of the invention is fluid catalytic cracking (FCC).
FCC technology, now more than 50 years old, has undergone continuous improvement and remains the predominant source of gasoline production in many refineries. This gasoline, as well as lighter products, is formed as the result of cracking heavier, less valuable hydrocarbon feed stocks such as gas oil.
In its most general form, the FCC process comprises a reactor that is closely coupled with a regenerator, followed by downstream hydrocarbon product separation. Hydrocarbon feed contacts catalyst in the reactor to crack the hydrocarbons down to smaller molecular weight products. During this process, coke tends to accumulate on the catalyst which is burned off in the regenerator.
It has been recognized that due to environmental concerns and newly enacted rules and regulations, saleable petroleum products must meet lower and lower limits on contaminates, such as sulfur and nitrogen. New regulations require essentially complete removal of sulfur from liquid hydrocarbons that are used in transportation fuels, such as gasoline and diesel.
Hydroprocessing is a process that contacts a selected feedstock and hydrogen-containing gas with suitable catalyst(s) in a reaction vessel under conditions of elevated temperature and pressure to remove heteroatoms such as sulfur and nitrogen from hydrocarbon streams to meet fuel specifications and to saturate olefinic compounds. Hydroprocessing is also used to prepare fresh hydrocarbon feed for FCC processing by demetallizing the FCC feed. Vanadium and nickel in the FCC feed can deactivate the FCC catalyst during the FCC process.
The demand for diesel has increased over gasoline in recent years. Petrochemicals such as propylene and single ring alkyl aromatics are considered even more valuable. Light Cycle Oil (LCO) is also produced in an FCC unit and can be directed to the diesel pool. However, LCO may degrade the quality of the diesel pool due to its high aromaticity and low cetane value. Upgrading of LCO to petrochemicals would be desirable.
Heavy Cycle Oil (HCO) is also produced in the FCC unit with little use other than for fuel oil. Further conversion of the HCO to motor fuel products would also be desirable.